package servlet;

import pojo.User;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

@WebServlet(urlPatterns = {"/user"})
public class UserServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("进入后台");
        List<User> users = new ArrayList<>();
        //jdbc操作数据库 查询
        //1、加载驱动
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");

            //2.获取连接()
            String url = "jdbc:mysql://127.0.0.1:3306/jdbc?characterEncoding=utf-8";
            Connection connection = DriverManager.getConnection(url, "root", "z2050115");
//            if(connection != null) {
//                System.out.println("连接成功");
//            }
            //3.写sql
            String sql = "select * from user";

            //4.预编译sql
            PreparedStatement preparedStatement = connection.prepareStatement(sql);

            //5.有参数设置参数

            //6.执行sql
            ResultSet resultSet = preparedStatement.executeQuery();

            //7.遍历结果集
            while (resultSet.next()) {
                User user = new User();
                user.setId(resultSet.getInt(1));
                user.setName(resultSet.getString(2));
                user.setPassword(resultSet.getString(3));
                //把对象添加到集合中
                users.add(user);

            }

            //8.关闭资源
            resultSet.close();
            preparedStatement.close();
            connection.close();


            //把集合中数据存储到作用域中
            req.setAttribute("users", users);
            //打开页面
            req.getRequestDispatcher("/user.jsp").forward(req, resp);


        } catch (ClassNotFoundException e) {
            throw new RuntimeException(e);
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }

    }
}

